Study On Irradiation And Switching Reliability Of SiC VDMOSFET

The Silicon Carbide MOSFET has been noticed widely as the next-generation electronics due to its excellent characteristics such as high critical breakdown voltage,high power density,and high thermal conductivity.Compared with the Si-based MOSFET the Si C MOSFET has a thinner epitaxial layer owing above characteristics.So,the Si C MOSFET device has a smaller on-resistance to reduce the loss of the system.With the further development of space explorations,the Si C MOSFET device is applied to some equipment gradually becoming a reality,but there are lots of high-energy particles in the deep space environment.The device’s working state will be changed when the high-energy particles through the device.In addition,a part of the energy stored in the parasitic inductor of the circuit will be released on the device,resulting in device damage.Therefore,if the Si C device will be used in the space field,we need to strengthen its radiation resistance.In response to the above requirements,the article mainly carries out the following works:Firstly,designing the structural parameters of basic VDMOSFET as required.Then the simulation software is used to simulate the basic electrical characteristics of the device,the results are compared with those that had been reported to prove the rationality of its.The heavy-ion incidence simulation was performed to find the most sensitive position of the VDMOSFET.And the lattice temperature is used to indicate the state of the device in this thesis.Secondly,the radiation characteristics of the device with four buffer layers are simulated,and the results show that the very high electric field at the drift/substrate is reduced,and the irradiation ability is strengthened.But the electric field in the oxide reached a high value because there is no Pshielding at the JFET region and the lattice temperature in the device is more than the Si C melting point.Based on the analysis of the results of the FB-VDMOSFET device,a novel structure called DTPN-VDMOSFET is proposed,which has two trenches in the source region and P-shielding at the bottom of trenches,integrated PN junction at the JFET region.We find that the CSL not only reduces the on-resistance but also improves irradiation ability.The termination of the DTPN-VDMOSFET device was optimized and the radiation characteristics were simulated by the TCAD.Finally,the characteristics of the unclamped inductive switch(UIS)of Si C conventional VDMOSFET are simulated,and the avalanche tolerance is calculated under certain conditions.The internal mechanism of device failure caused by the UIS process is also analyzed and proved.